Manufacture of potassium carbonate



0d. 31, 1933. F, RUSBERG 1,933,452

MANUFACTURE OF POTASSIUM CARBONATE Filed Aug. 10, 1932 1m we @1505 5140fa@ ma l?? 7/Zm/@4 Patented vm31.193s i' l l f 1,933,452.`

MANUFACTURE OF POTASSIUM CARBONATE y Friedrich Rs'berg, u BerlinNiederschoneweide,

Germany, assignor to Kali-Chemie, Aktiengesellschaft, Berlin, GermanyApplication August 10,r 1932, Serial No. 628,258, y. and in GermanySeptember 29, 1931.

12 claims. (ci. ,2s-s3) l This invention relates to the manufacture of Afurther object of the invention is to provide potassium carbonate frompotassium salts of for a continuous regeneration treatment of the strongmineral acids and magnesium carbonate cycling magnesium carbonatetrihydrate. tlhydrate. l p Still a further object of the invention istoIt is known to make potassium carbonate by maintain the cyclingmagnesium carbonate tri- 60 treating with carbon dioxidea suspension ofmaghydrate by Vpartial regeneration as long as posnesium carbonatetrihydrate in an aqueous solu- 1 sible in such a state of purity, thatthe production tion of potassium chloride, whereby a` crystal of Engelsalt is not disturbed by the use of the water containing double salt ofpotassium bicarcycling trihydrate. y

bonate and magnesium carbonate, named Engel According to the inventionthe regeneration of 65 salt, precipitates, which on decomposition withthe impure magnesium carbonate trihydrate obwater at raised temperaturefurnishes an aqueous tained by the decomposition of Engel salt is car-`solution of potassium bicarbonate, which may ried out by converting itinto the water soluble contain potassium carbonate and solidmagnemagnesium bicarbonate by treatment with car-- sium bicarbonatetrihydrate, which is used again bon dioxide in presence of water andrecovering 70 for the manufacture of potassium carbonate magnesiumcarbonate trihydrate from the bicarfrom fresh potassium chloride. Thisprocess, in bonate solution obtained, by heating the solution which thepotassium chloride may be replaced by or by neutralizing the bicarbonatewith caustic y potassium salts of other strong mineral acids, magnesia,thus precipitating magnesium carbon.

such asA potassium sulfate, is called Engel-Precht ate trihydrate. Bythe treatment of the impure 75 vmethod and supposed to take placeaccording to trihydrate with carbon f dioxide in presence of thefollowing equations: 1 Water also the basicmagnesia present asimpurity 1) 2Kc1+3 Mgoo3en2 +oo2+n2o= 1 the tlhylfategs Cnverfeelotaeo 2KHC03-MgCo3AH2o +MgC12+H2omagnistum wat ma e' W I lmpuritles mayberemoved by separating them 80 2) KHCOSMgCOSAHzo-FHZO:

from the magnesium bicarbonate solution ob- MgCO3'3H2O+KHCO3+2H2O'tained as intermediateproduct inthe regenera- The magnesium CalbOnatetlhydrate Obtained tion treatment. The regeneration of the impure by thedecomDOStOn 0f the Engelsalt always magnesium carbonate trihydrateobtained by decontains some basic magnesia, which is not ablecomposition of Engel salt may be Carried Out 85 to form Engel salt withfresh potassium chloride,- periodically after this trihydrate has beenused When TBUSDg the magnesium CalbOnate l'ihyseveral times in thecyclic process, or continudate Obtained. by the deCOmDOStOIl 0f Engelously, by regenerating always a part of the trisalt for the processagain. After several cycles hydrate obtained by each decompositiontreatof this recovered magnesium carbonate trihydrate ment of freshlyproduced Engel salt and using 90. i138 @Ontent 0f basic magnesio andOther Solid the regenerated magnesium carbonate trihydrate impuritiesbecomes so high, that serious diicul-`V together with the notregenerated part of trities in the formation of fresh Engel saltoriginate. hydrate in a cycle. This continuous partial re- It is thenusual to remove the cycling magnesium generation is the preferred formofthe invention,

40 carbonate trihydrate from the processor to reas it (mames to maintainthe trihydrate of mag- 95 generate it. ThiregenelaOn iS Carried out bynesium carbonate obtained by the decomposition calcinins the impuretrhydrate at temperatures of Engel salt for a long time in suon a stateof far above 1000 C., thus Obtaining Caleined maspurity, `that `it doesnot disturb the formation of nesia, which is hydratedy and thenconverted -into fresh Engel Salt, when reusing it in the process.

magnesium carbonate trihydrate by treatment with carbon dioxide inpresenceof Water. This Exemples regeneration treatment affords specialfurnaces 1 Engel salt, containing about 13% MgO and other devices and isvery expensive. -and 20% KzCOz and obtained in the usual man- The mainobject of the present invention is to ner by treating with carbondioxide a suspenreplace the above described expensive regenerasion ofmagnesium carbonate trihydrate in an tion treatment of the cyclingmagnesium carbonaqueous solution of potassium chloride, is decomatetrihydrate by a simple and effective, cheaper posed by treatment withwater at about 40 to process, which does not afford the employment of C.The solution of potassium bicarbonate high temperatures and calciningfurnaces and obtained,which solution may contain potassium 5.5 votherspecial devices. y carbonate, is separated from the solid magnesium terat raised temperatures, separating fthe" liquid decomposition product,being an aqueous solution ofv potassium salts of carbonic acid, from thesolid decomposition product; being impure magnesium carbonatetrihydrate, convertingat least a part ofthe magnesium carbonatetrihydrate, obtained'by the decomposition, into magnesium bicarbonateVby treatmentwith carbon dioxide in presence of Water, converting'themagnesium bicarbonate obtained into magnesium carbonate trihydrate andreturning the magnesium carbonate trihydrate into the process for makingpotassium salts 'of carbonio acid from fresh potassium salts of strongmineral acids.

5. A method for making potassium salts of carbonic acid which consistsin treating with carbon dioxide a suspension of magnesium carbonlformedfrom the liquid obtained, decomposing the separated double salt bytreatment with Water at raised temperatures, separating the liquid de--composition product, being an aqueous solution of potassium salts ofcarbonic acid,from the solid :decomposition product, being impuremagnesium carbonate trihydrate, converting the magnesium carbonatetrihydrate, obtained by ,thedecompo-l, sition,` into magnesiumbicarbonate by treatment with carbon dioxide in presence ofvvater, con-vverting the magnesium bicarbonateobtained into magnesium carbonatetrihydrate and returning the magnesium carbonate vtrihydrate into -theprocess for making potassium salts of carbonio acid yfrom freshpotassium'salts of strong mineral acids.

A6. A method for making potassium salts of carbonio acid which consistsin treating with carbon dioxide a suspension 'of magnesium carbonatetrihydrate in an aqueous solution of potassiumchloride, separating thesolid double salt formed from the liquidobtained, decomposing theseparated double salt by treatment with Water at raised temperatures,separating the liquiddecomposition product, being an aqueous solution ofpotassium salts of carbonio acid, from the solid decomposition product',being impure magnesium carbonate trihydrate, converting a part of themiagnesium carbonate trihy'dr'ata obtained by-r the decomposition vintomagnesium bicarbonate 5 by treatment With carbon dioxidein presence ofWater, converting the magnesium bicarbonate obtained into magnesiumcarbonate trihydrate `and 7. A method for making potassium salts of car-K bonic acid which consists in treating with carbon *dioxide asuspension' of magnesium carbonate trihydrate in an aqueous solution ofpotassium salts of Astrong fmineral acids, separatingv the solid doublesalt formed from the liquid-obtained,

decomposing `the separated double salt `by treatl ment with Water atraised temperatures, separating the liquid decomposition product, beingan aqueous solutionl of potassiumsalts of carbonio acid, from the soliddecomposition product, be-l ing impure magnesium carbonate trihydrate,converting at least apart of the magnesium carbonate trihydrate,obtained by the decomposition,

into magnesiumqbicarbonateby treatment with carbon dioxide in presenceof Water, converting `the aqueous solution of magnesium bicarbonate`obtainedinto precipitated magnesium carbonate trihydrate by 'heatingland returningr the magnesium carbonate trihydrateinto the process-formakingfpot'assiu'm' salts ofvcarbonicv acid from fresh potassium saltsof 'strongmineral acids.

8. `A method for making potassium salts of carbonio acid which consistsin treating with carbon lsc dioxidea-suspension'of,magnesium.carbonateftrihydrate inan aqueous solutionofpotassium salts of strong mineral acids, separating the solid doublesalt formed from 'theliquid obtained, decomposing the separated doublesalt by treatment 'with Water at raised'.,temperatures,separating theleast a part ofthefm'agnesium carbonate trihydrate, obtained by thedecomposition, into magy nesium bicarbonate by treatment with` carbon`dioxide in presence^of Water,y converting the aqueous solution ofmagnesium bicarbonate oby tained intoI precipitating magnesium carbonatetrihydrate byneutralizing it with caustic magnesia and returning themagnesium carbonate tri-y 'hydrate into `the process for makingpotassium salts of carbonio acid from vfresh potassium vsalts Vof strongmineralacids. i

9. In the cyclic manufacture` of potassium carbonate from potassiumsalts of strong mineral acids according tothe method `of Engel-Prachtthe steps of regenerating the impure magnesium carbonate trihydrate,obtained by decomposition of Engel salt, by converting it into an,vaqueous iis acids according to the method of Engel-'Precht ther v stepsof regenerating a part of the, impure magnesium vcarbonate trihydrate,obtained by each decomposition of Engel salt, by converting it into vanaqueous solution of magnesium bicarbonate,

separating the solid residue from the solution, re`

covering magnesium carbonate trihydratefrom L the solution and reusingthis trihydrate together With the not regenerated part of ,decompositiontrihydrate for makingl fresh Engel salt.l

- 11. A method for regenerating impure mag-l position of Engel salt Withwater which consists in treating said magnesium carbonate trihydratewith carbon dioxide in presence of water at super- .nesium carbonatetrihydrate obtained by decomf atmospheric pressure, separating the-aqueous g solution of magnesium bicarbonate vobtained from the residueand converting the bicarbonatefo magnesium into magnesiumcarbonatetrihydrate.

12. A continuousmethod for making potassium 2:.-

carbonate from vpotassium lchloride and magnesium carbonate trihydrateaccording to Engel- Precht Which consists in treating with carbondioxide a suspension of magnesium carbonate trihydrate in an aqueoussolution of potassium chloride, separating the solid productiormed from'the solution of magnesium chloride obtained,

treating the separated solid product with Water dluted aqueous solutionof magnesium bicarbonate with carbon dioxide at a superatmosphericpressure, separating the aqueous solution of magnesium bicarbonateobtained from solid residue,

5 heating said. solution to precipitate purified magnesum carbonatetrhydrate and reusing the puried. magnesium carbonate trhydrate to-`gether with thevremaning part of impure magnesum carbonate trhydrate,obtained by de,-

